Optical sensor having directional sensitivity

ABSTRACT

An apparatus includes a light senor having directional sensitivity. The light sensor includes multiple light sensitive elements disposed below the same aperture. Each of the light sensitive elements has a respective field of view through the aperture that differs from the field of view of the other light sensitive elements. Signals from the light sensor can facilitate determining the direction of incoming light.

FIELD OF THE DISCLOSURE

This disclosure relates to optical sensors having directionalsensitivity.

BACKGROUND

Various consumer electronic products such as smart phones and otherportable host computing devices include compact optoelectronic modulesthat have integrated light sensing and/or light emitting devices. Someof these modules are configured to determine the direction from which alight signal is received.

SUMMARY

The present disclosure describes an apparatus that includes a lightsenor having directional sensitivity. The light sensor includes multiplelight sensitive elements disposed below the same aperture. Each of thelight sensitive elements has a respective field of view through theaperture that differs from the field of view of the other lightsensitive elements.

In some implementations, the apparatus also includes an electroniccontrol unit operable to determine a direction of received light basedon output signals from one or more of the light sensitive elements andbased on the respective fields of view of the light sensitive elements.

In some cases, the light sensitive elements are disposed across an arealarger than a cross-sectional area of the aperture. The light sensitiveelements can be implemented, for example, as pinned diodes, althoughtypes of photodetectors can be used as well. In some implementations,the light sensitive elements form a two-dimensional array ofphotodetectors.

In some instances, at least some of the respective fields of view of thelight sensitive elements partially overlap one another.

The light sensitive elements may be formed, for example, in asemiconductor substrate, and the apparatus can include at least onemetal layer having an opening that defines a size of the aperture. Inother implementations, a black mask filter or other layer has an openingthat defines the size of the aperture.

The light sensor can be disposed, for example, in a portable hostcomputing device (e.g., a smartphone, tablet, wearable device, personaldigital assistant (PDA), or personal computer). Depending on theapplication, the electronic control unit can be operable to useinformation about the determined detection in conjunction with gesturerecognition, proximity sensing, ambient light sensing, color sensing,and/or time-of-flight (TOF) sensing. In some instance, the electroniccontrol unit is operable to process the signals from the light sensitiveelements to determine whether the received light is diffuse or whetherthe received light is coming from more than one source.

In some implementations, the optical sensor can be ultra-small and canachieve improved directional sensitivity at a relatively lowmanufacturing cost.

Other aspects, features and advantages will be readily apparent from thefollowing detailed description, the accompanying drawings, and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a sensor module.

FIG. 2 is a schematic side view of a light sensor.

FIG. 3 is a schematic top view of the light sensor.

FIG. 4 illustrates further details of the light sensor according to aparticular implementation.

DETAILED DESCRIPTION

In general, an optoelectronic module as described in this disclosure hasa light sensor, and also may include an illumination source, each ofwhich may be implemented, for example, in a respective die (e.g., anintegrated circuit semiconductor chip). In some instances, lightproduced by the illumination source is emitted from the module toward anobject that reflects a portion of the light back toward the module whereit may be detected at the light receiver. In some instances (e.g., forgesture recognition), it is desirable to be able to detect the directionfrom which the light detected in the module is received.

FIG. 1 illustrates an example of a sensor module 10 that includes anillumination source 12 operable to produce light, and a light sensor 14operable to sense light of a wavelength (e.g., infra-red (IR), near IR,visible or ultraviolet (UV)) produced by the illumination source 12. Theillumination source can include one or more light emitters, examples ofwhich include light emitting diodes (LEDs), infra-red (IR) LEDs, organicLEDs (OLEDs), infra-red (IR) laser diodes, vertical cavity surfaceemitting lasers (VCSELs)) and arrays of such devices. In some cases, themodule includes passive optical components to redirect light byrefraction and/or diffraction and/or reflection (e.g., a lens, a prism,a mirror). The dies for the illumination source 12 and light sensor 14can be mounted and electrically coupled to a printed circuit board (PCB)18 of a host device (e.g., a portable computing device such as asmartphone, tablet, wearable device, personal digital assistant (PDA),or personal computer). The electrical connections may be include one ormore of die pads, surface mount connections, wire bonds or solder balls,depending on the implementation.

In the illustrated example, the illumination source 12 and light sensor14 are surrounded laterally by a spacer or housing wall 20 that, in somecases, is opaque to the wavelength(s) produced by the illuminationsource 12 and sensed by the light sensor 14. An interior wall 22 canseparate the illumination source 12 and light sensor 14 from oneanother, which can help reduce internal optical crosstalk. In someimplementations, the interior wall 22 may not be present. The module 10can be disposed, for example, behind the backside 25 of a cover glass 24of the host device.

To provide directional sensitivity, the light sensor 14 includesmultiple light sensitive elements (i.e., two or more) disposed below thesame aperture such that each of the optically sensitive elements has afield of view (FOV) that differs from the FOV of the other opticallysensitive elements. FIGS. 2 and 3 illustrate an example, discussed ingreater detail below.

As shown in FIGS. 2 and 3, the light sensor 14 includes multiple lightsensitive elements 30 (i.e., two or more) disposed below the sameaperture 32. The light sensitive elements 30 can be implemented, forexample, as pinned diodes, photodiodes, single-photon avalanche diodes(SPADs), or other light detecting devices. In some instances, pinneddiodes are particularly advantageous because of their small size. Forexample, for some mobile camera sensors, the pixel size may be about 1.1μm×1.1 nm. Different sizes, including smaller pinned diodes (e.g.,0.2μ×0.2 nm), can be used in other implementations. The light sensitiveelements 30 can be arranged, for example, as an M×N array (where each ofM and N is greater than 1) or as a linear array. FIG. 3, for example,shows a 3×4 array of light sensitive elements 30, although size arrayscan be used as well. In other cases, the light sensitive elements 30 canbe arranged in some other configuration.

Collectively, the light sensitive elements 30 should be disposed acrossan area (i.e., in a plane parallel to the plane of the substrate 18)larger than the cross-sectional area of the aperture 32 (see, e.g., FIG.3). In this way, each light sensitive element 30 has a FOV that differsfrom the FOV of the other light sensitive elements. FIG. 2 shows the FOV34 for one of the light sensitive elements 30. Although the respectiveFOVs of the light sensitive elements 30 differ from one another, theymay overlap partially.

As illustrated in FIG. 4, the aperture 32 can be defined by depositingone or more metal layers 36 directly on the semiconductor (e.g.,silicon) substrate in which the light sensitive elements are formed.FIG. 4 illustrates the respective FOV 34A, 34B, 34C for each of threelight sensitive elements 30A, 30B, 30C. In the illustrated example, thetop metal layer 36A has an opening that defines the size of the aperture32. In some instances, the distance between the photosensitive siliconsurface and the top metal layer 36A is about 1 nm. Different values maybe appropriate for other implementations. One advantage of forming theaperture by a stack of one or more metal layers is that it allows theaperture to be formed using standard CMOS processes. Nevertheless, insome implementations, the aperture can be formed in other ways. Forexample, the aperture 32 can be defined by a small opening in a blackmask filter (e.g., if the distance to the light sensitive elements isrelatively large such as in the range of 5-10 nm). In otherimplementations, the aperture 32 can be defined using some other layerthat can block incoming light (e.g., a white or reflecting filter).

The signal(s) sensed by the light sensor 14 can be read out andprocessed by an electronic control unit (ECU) 28 (see FIG. 1) either inthe sensor module 10 itself or in the host device in which the module isdisposed. The ECU 28 can be implemented, for example, as an integratedcircuit chip or other processor and may include software stored inmemory. The ECU 28 may include appropriate logic and/or other hardwarecomponents (e.g., read-out registers; amplifiers; analog-to-digitalconverters; clock drivers; timing logic; signal processing circuitry;and/or microprocessor). In some cases, the ECU 28 (or part of it) can beintegrated into the same IC chip as the light sensor 22.

The ECU 28 is operable, among other things, to determine a directionfrom which the detected light was received in the module 10. This can beaccomplished, for example, by identifying which of the light sensitiveelements 30 generated the largest output signal (e.g., after accountingfor noise or optical cross-talk) and using that information togetherwith stored information about the FOV for the particular light sensitiveelement 30 to identify the direction of the incoming light. In somecases, more than one of the light sensitive elements 30 may detect asignal during the same period. The ECU 28 then can analyze the signalsoutput by the light sensitive elements 30 based, for example, on therelative amplitudes of the signals and to use that information, togetherwith the stored knowledge of the FOVs for the light sensitive elements,to estimate the direction from which the detected light was received. Insome instances, the ECU 28 is operable to process the signals from thelight sensitive elements 30 to determine whether the light is diffuse orcoming from one or more sources (e.g., spotlights).

Knowledge of the direction from which the light is received can increasethe information available to the ECU 28 about the detected light. Suchknowledge can be used in a range of different applications including,for example, gesture recognition, proximity sensing, ambient lightsensing, color sensing and time-of-flight (TOF) and distance sensing.

Gesture recognition, for example, has become prominent in portable andwearable devices in the gaming, healthcare, automation, automotive andconsumer electronics sectors. In the context of gesture recognition, theECU 28 can provide a perceptual computing user interface that allows thedevice to capture and interpret human gestures as commands in acontactless manner. For example, the ECU 28 can use the directionalinformation obtained from the light sensitive element output signals,together with other information, to determine the physical motion of theuser's finger or hand. The techniques described above for the lightsensor 14 can, in some cases, facilitate an ultra-low cost solution thatdoes not require optical lenses or special packaging. The small size canbe particularly suited, for example, for earbuds, where gesture sensorscan be used to control the sound (e.g., loudness, mute, or switch off)without requiring the user to touch the device.

In the context of proximity sensors, knowing the direction from whichthe detected light is coming can, in some instances, help distinguishwhich portions of the received light come from crosstalk, reflectionsfrom the host device' cover glass or a smudge on the cove glass, or froma target in front of the host device

In the context of ambient light sensors, knowing the direction fromwhich the detected light is coming can, in some cases, help determinehow strong reflections may be and to what extent the ambient light maytend to blind the user of the host device. The ECU 28 can be configuredwith an intelligent algorithm to adjust, for example, the brightness ofthe host devices' display screen based on the ambient light conditions.

In the context of color sensors (e.g., red, green, blue and clear),knowing the direction from which the detected light is coming can, insome cases, help the ECU 28 estimate the color temperature of the lightcoming from different directions. For near-perfect white balance, adetailed knowledge about the light conditions can provide a significantadvantage. Such knowledge might indicate, for example, that there isdiffuse light or strong light on one side.

In the context of TOF sensors, knowing the direction from which thedetected light is coming can, in some cases, allow the sensor toidentify the targets in different directions, which can facilitate anultra-low cost, multi-zone sensor in which lenses are not required.

The foregoing types of sensors can be integrated, for example into asmartphone or other portable host computing device (e.g., tablet,wearable device, personal digital assistant (PDA), or personalcomputer). The design of such devices referenced can include one or moreprocessors, one or more memories (e.g. RAM), storage (e.g., a disk orflash memory), a user interface (which may include, e.g., a keypad, aTFT LCD or OLED display screen, touch or other gesture sensors, a cameraor other optical sensor, a compass sensor, a 3D magnetometer, a3-axisaccelerometer, a 3-axis gyroscope, one or more microphones, etc.,together with software instructions for providing a graphical userinterface), interconnections between these elements (e.g., buses), andan interface for communicating with other devices (which may bewireless, such as GSM, 3G, 4G, CDMA, WiFi, WiMax, Zigbee or Bluetooth,and/or wired, such as through an Ethernet local area network, a T-1internet connection, etc.).

Various aspects of the subject matter and the functional operationsdescribed in this specification (e.g., those related to the circuitry28) can be implemented in digital electronic circuitry, or in computersoftware, firmware, or hardware, including the structures disclosed inthis specification and their structural equivalents, or in combinationsof one or more of them. Thus, aspects of the subject matter described inthis specification can be implemented as one or more computer programproducts, i.e., one or more modules of computer program instructionsencoded on a computer readable medium for execution by, or to controlthe operation of, data processing apparatus. The computer readablemedium can be a machine-readable storage device, a machine-readablestorage substrate, a memory device, a composition of matter effecting amachine-readable propagated signal, or a combination of one or more ofthem. The apparatus can include, in addition to hardware, code thatcreates an execution environment for the computer program in question,e.g., code that constitutes processor firmware.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Computer readable media suitable forstoring computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments of the invention. Certain features that are described inthis specification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or variation of a sub-combination.

A number of implementations have been described. Nevertheless, variousmodifications may be made without departing from the spirit and scope ofthe invention. Accordingly, other implementations are within the scopeof the claims.

1. An apparatus comprising: a light sensor having directionalsensitivity, wherein the light sensor includes a plurality of lightsensitive elements disposed below a same aperture, wherein each of thelight sensitive elements has a respective field of view through theaperture that differs from the field of view of the other lightsensitive elements.
 2. The apparatus of claim 1 further including anelectronic control unit operable to determine a direction of receivedlight based on output signals from one or more of the light sensitiveelements and based on the respective fields of view of the lightsensitive elements.
 3. The apparatus of claim 1 wherein the lightsensitive elements are disposed collectively across an area larger thana cross-sectional area of the aperture.
 4. The apparatus of claim 1wherein the light sensitive elements comprise pinned diodes.
 5. Theapparatus of claim 1 wherein at least some of the respective fields ofview of the light sensitive elements partially overlap one another. 6.The apparatus of claim 1 wherein the light sensitive elements are in asemiconductor substrate, the apparatus further including at least onemetal layer having an opening that defines a size of the aperture. 7.The apparatus of claim 1 including a black mask filter having an openingthat defines a size of the aperture.
 8. The apparatus of claim 1 whereinthe plurality of light sensitive elements is a two-dimensional array ofphotodetectors.
 9. The apparatus of claim 1 wherein the light sensor isdisposed in a portable host computing device.
 10. The apparatus of claim2 wherein the electronic control unit is operable to use informationabout the determined detection in conjunction with gesture recognition.11. The apparatus of claim 2 wherein the electronic control unit isoperable to use information about the determined detection inconjunction with proximity sensing.
 12. The apparatus of claim 2 whereinthe electronic control unit is operable to use information about thedetermined detection in conjunction with ambient light sensing.
 13. Theapparatus of claim 2 wherein the electronic control unit is operable touse information about the determined detection in conjunction with colorsensing.
 14. The apparatus of claim 2 wherein the electronic controlunit is operable to use information about the determined detection inconjunction with time-of-flight (TOF) sensing.
 15. The apparatus ofclaim 2 wherein the electronic control unit is operable to process thesignals from the light sensitive elements to determine whether thereceived light is diffuse.
 16. The apparatus of claim 2 wherein theelectronic control unit is operable to process the signals from thelight sensitive elements to determine whether the received light iscoming from more than one source.
 17. An apparatus comprising: a lightsenor having directional sensitivity, wherein the light sensor includesan array of pinned diodes disposed below a same aperture, wherein eachof the pinned diodes has a respective field of view through the aperturethat differs from the field of view of the other pinned diodes, whereinthe pinned diodes collectively are disposed across an area larger than across-sectional area of the aperture; at least one metal layer having anopening that defines a size of the aperture; and an electronic controlunit operable to determine a direction of received light based on outputsignals from one or more of the pinned diodes and based on therespective fields of view of the pinned diodes.